Process for the recovery of tin compounds in the art of loading silk



Sept. 20, 1932.- w, MEH'NER 1,878,507

PROCESS FOR THE RECOVERY OF TIN COMPOUNDS IN THE ART OF LOADING SILK Filed De c. 11, 1931 fa con/ainer for Na; 5h 85 'SOIu/lbn fo'receiw'ng vessel l fbr phospha/e freed from fin 1% r/S QS' I Patented Sept. 20, 1932 UNITED STATES WALTER MEITNER, OF=VIE1 \TNA, -AUSTRIA PROCESS FOR THE RECOVERY or rm COMPOUNDS in THE ART or LoAnrric smx Application filed December 11, 1931, Serial No. 580, 4Z1.and in Austria December 9, 19 30.

The invention relates to the recovery oftin compounds in the art of loading silk.

When silk istreated so as to become loaded by adding to the fibres stannic chloride, wash- Q. ing with water and subsequently treating with di-sodium-phosphate the excess stannic chloride is precipitated on the surface of the silk and passes into the remaining phosphate baths which thus contain 1 part per thousand of metallic tin. The recovery if any of this tin has hitherto been rather incomplete.

The invention relates to a sim 1e process for separating out from phosphate baths the tin which they have taken up and which impairs their further application, such recovery being performed without losses of phosphate. All the methods of purification hitherto proposed are expensive and involve high losses of phosphate. The present proc- 20 ess allows of a complete recovery of tin in an inexpensive manner because it works with; out application of fuels and chemicals. It simply consists in passing the liquid under treatment through a filtering device which has an absorbing action on tin compounds, Whereas it allows to pass the other substances dissolved in the liquid without altering the same. I i

As a suitable filtering material I may use active aluminium hydroxide by itself or substances containing such aluminium hydroxide. V The use of aluminium hydroxide as an active filtering material is already known. Sometime ago it has been proposed to use precipitated or washed alumina for decolorizing or deodorizing liquids. Moreover active alumina has been applied for drying gases and vapors and for dehydrating liquids. For this purpose aluminium hydroxide is suitable which has been pressed to solid pieces and has been heated to 4:00 to 600 C. Aluminium hydroxide which has been heated to higher temperatures has also been proposed as an ing a hydroxyl group such as alcohols, phenols and the like. I

For the purification of phosphate baths and the simultaneous recovery of tin in an inexpensive manner actlvated alumlnlum adsorbing means for organicsubstances havhydroxide is used according to the invention 'Whichis preferably prepared by decompos- 'issi'milar to the filtering devices used in the purification'of. waterand which is'illus'trated 1n the accompanying drawing.-

'Ifthe phospliate baths are passed through such afilterwithout being heated the filter completely adsorbs the tin and merelyretains somephosphoric" acid in the'b'eginning' of the filtering process, which is, however, dis'solvedflater on by further quantities of the liquid underfiltrationor by a subsequent washingwith water. p

or the recovery of tin and a simultaneous reactivation of the filtering device the latter is washed withl-"a solution of sodium sulphide towhich'sulphur has been previously added. In-this manner a solution of sodium sulpho-stannate'is' formed from which'the tin may be; precipitated by acidifying the solution. f r 'i The inventionis illustrated by the following example; i 250 liters ofp'hosphate bath3-containing 0.4g. Sn per liter'are passedduifing 5' hours over 10 kgs. of activated aluminium hydroxide havinga water content of 68 per cent. The filtrate is freefromjltin. The: filter is then washed with the solution of 0.8 kgs. NagS.9H O+0.1 to 0.2 kgs. sulphur in 8 litersof water; The filtrate contains the whole amount of tin contained in the phosphate bath. r In theaccompanying drawing 1 designates a container for the' filtering material 2. Near the bottom of said container is arranged a sieve 3 covering a layer of gravel 4, :in which an inlet pipe 5 perforated at 15 is embedded; This pipe is' provided with a shut-off valve 6. Pipe 7 branching off from pipe 5 and controlled by a valve 8 allows to introduce the solution'into the filter from' the top by means of a spray 9. The container 1 is fitted with an overflow pipe 10. At the.

bottom of the container 1 an emptying pipe 11 with a valve 21 is provided, from which conduits 12 and 13 controlled by valves 22 and 23 lead to the container for the Na SnSS solutions and to thereceiving vessel for the phosphate freed from tin respectively.

In operation the phosphate solution to be freed from tin is supplied through pipe 5 either by gravity or by means of a pump or by air pressure; valve 6 is closed, valve 8 be-' ing open; the solution rises through pipe 7 to spray 9, from where it is distributed over the surface of the filtering material 2. Thesolution passes through said filtering material where it deposes its Sn contents and leaves the container through sieve 3, gravel layer 4 and the pipe 13 to the receiving vessel, valve 23 being open, valves 22 and21 being closed. Y

To reactivate the filtering mass and to recover the tin contained therein a solution of Na S +sulfur is introduced into the container 1 alternatively through spray 9 and/or through the perforated pipe 15, valves 8 and 6 being open or closed respectively. The tin forms with said solution Na SnS this latter solution being allowed to flow through the open valve 22 into a container, where Sn is set free by acidification. During this operation valves 21 and 23 are closed.

What I claim is 1. A process for recovering tin from waste phosphate baths in the art of loading silk which comprises passing the said Phosphate baths through a filtering device charged with active aluminium hydroxide removing the filtrate and washing the filtering device with a solution capable of dissolving the tin.

2. In a process for recovering tin from waste phosphate baths in the art of loading silk, the step which comprises passing the said phosphate baths through a filtering dey vice-charged with aluminium hydroxide having a water content of 50 to per cent.

3. In a process for recovering tin from waste phosphate baths in the art of loading silk, the step which comprises passing the said phosphate baths through a filtering device charged with active aluminium hydroxide being in a granular state.

4. A process for recovering tin from waste phosphate baths in the art of loading silk which comprises passing the said phosphate baths through a filtering device charged with active aluminium hydroxide removing the filtrate and washing the filtering device with gdsolution containing sulfur and sodium sul- In testimony whereof, I afiix my signature.

WALTER MEITNER. 

